Method of making a tobacco extract

ABSTRACT

The invention concerns a method of obtaining a concentrated tobacco extract, for use in a smoking material, from a dilute aqueous extract in which reverse osmosis is applied to the dilute extract, using a membrane substantially impermeable to the solute components of the extract. The reverse-osmosis process may be performed at substantially ambient temperature and at a pressure within the range of from 39 to 49 kg/cm2.

United States Patent [1 1 Molyneux METHOD OF MAKING A TOBACCO EXTRACT [75] Inventor: David J. Molyneux, Southampton,

England [73] Assignee: Brown & Williamson Tobacco Corporation, Louisville, Ky.

[22] Filed: Feb. 22, 1973 [21] Appl. No: 334,687

[30] Foreign Application Priority Data Mar. 6, 1972 Germany ..l03l1 [52] US. Cl. 131/143, 2lO/22 [51] Int. Cl..... A24b 15/08 [58] Field of Search 131/140-144, l31/l7; 210/22, 99

[56] References Cited UNITED STATES PATENTS Moonelis 131/143 X Nov. 12, 1974 3,l45,7l7 8/1964 Osborne el ill, l3l/I43 X 3,228,876 H1966 Mahon 3,3l6,9l9 5/1967 Green et al. A, l3l/l43 Primary Examiner-Melvin D. Rein Attorney, Agent, or FirmFinnegan, Henderson, Farabow & Garrett [57] ABSTRACT The invention concerns a method of obtaining a concentrated tobacco extract, for use in a smoking material, from a dilute aqueous extract in which reverse osmosis is applied to the dilute extract, using a membrane substantially impermeable to the solute components of the extract, The reverse-osmosis process may be performed at substantially ambient temperature and at a pressure within the range of from 39 to 49 kg/cm 1 Claim, 1 Drawing Figure This invention concerns improvements relating to smoking materials, particularly but not exclusively such for use in cigarettes.

Some processes for the reconstitution of tobacco or the production of smoking material, particularly the widely used paper process, require the preparation of an aqueous tobacco extract at a concentration which exceeds that normally achieved with commercial extraction equipment. Processes which have been used and considered for the concentration of dilute aqueous tobacco extract include vacuum evaporation using various types of film evaporators, spray drying and freezedrying. These processes have the following disadvantages:

a. Thermal degradation of the tobacco solubles occurs, although this may not be marked in the case of freeze-drying.

b. Loss of volatile components occurs in all three processes.

c. The processes are costly, particularly freeze-drying and, at low outputs, vacuum evaporation.

d. Spray-drying requires a minimum feed concentration of at least percent.

Products containing extracts so concentrated, other than those obtained by freeze-drying, give a tobacco smoke of inferior taste and flavour.

The present invention seeks to provide simple and practicable means whereby these disadvantages can be avoided, so that tobacco extracts can be readily produced at concentrations suitable for use in smoking materials for modifying in required fashion the characteristics of the smoke obtained from the said materials.

We have found that an excellent tobacco extract can be obtained in concentrated form by applying the process of reverse osmosis. Osmosis is a process in which a solvent placed on the opposite side of a semipermeable membrane from a solution will pass through the membrane into the solution, tending to equalize the concentrations on the two sides of the membrane. The flow of solvent into the solution can be stopped by application of pressure to the solution. The pressure required to stop osmosis for any given solution is called the osmotic pressure of that solution. If the pressure applied to the solution exceeds the osmotic pressure, the direction of flow of the solvent will be reversed and the solution will become more concentrated. This is known as reverse osmosis. The pressure needed to achieve reverse osmosis increases with the concentration of the solution and with temperature.

According to the invention, for obtaining a concentrated tobacco extract, for use in a smoking material, from a dilute aqueous extract, the process of reverse osmosis is applied to the dilute extract, using a membrane substantially impermeable to the solute components of the dilute extract. Advantageously, the process is performed at substantially ambient temperature and at a pressure within the range of from 28 to 85 kg/cm preferably a range of from 39 to 49 kg/cm Reverse osmosis works well with a mixture of solutes in a common solvent, as is the case with an aqueous tobacco extract, providing that the membrane is impermeable to all the solute components of the mixture. Commercial membranes are in practice very slightly permeable to most solutes. Synthetic membranes can be constructed with widely varying characteristics as regards permeability to materials of differing molecular weight, flux rate (solvent-flow rate per unit area of membrane), permissible operating pressure, chemical compatibility and so forth. The application of the process of reverse osmosis to tobacco extracts in practice is therefore basically simple, requiring only the selection of a membrane suitable for the extracts and a support system in which membranes can operate satisfactorily for extended periods. Possible difficulties due to concentration polarization and the viscosity of the concentrated extract can be avoided in known manner by ensuring that flow conditions in the apparatus are sufficiently turbulent.

A concentrated tobacco extract can be thus obtained by means requiring low operating temperatures, in which thermal degradation is avoided and loss of volatile components is materially reduced. When a concentrated tobacco extract thus produced is added to natural tobacco, reconstituted tobacco or other smoke material or mixture, a smoking product can be obtained having improved smoking characteristics, especially improved taste and flavour.

One manner of carrying the invention into effect will now be more fully described, by way of example, with reference to the accompanying drawing which is a diagrammatic representation of a reverse-osmosis apparatus.

Dilute extract from a tobacco-extraction device is pumped through a line 1 to a feed tank 2 provided with a mixer 3. A transfer pump 4 feeds a high-pressure pump 5 at the required rate and at a positive pressure sufficient to enable the latter pump to operate effectively. The pump 5 passes the extract into an array of reverse-osmosis modules 6 at the required pressure, which may be up to kg/cm but is preferably in the range of from 39 to 49 kg/cm The unit shown has six tubular-type modules having the tubes connected in series both internally and between modules. A total membrane surface area of 10 m is provided. lf required, the modules can be operated individually, or in parallel or series-parallel, by rearrangement of the external piping. Each module contains eighteen 12.5 mm diameter perforated stainless steel tubes and each tube encloses a cellulose acetate membrane deposited on a paper support. The characteristics of the membrane can be altered to suit the characteristics of the extract being processed and the mebranes can be changed as required.

When the dilute extract is passed through the tubes at high pressure, reverse osmosis takes place, the water, known as permeate, passes through the membrane and is collected in a manifold 7 whence, by cocks 8 and 9, it can be discharged to a drain at 10 or, if required, recycled through a line 11 to the tank 2. The concentrated extract is retained in the tubes and is discharged from the final module 6 through a line 13 in which a manually controlled valve 14 is provided for regulating the pressure in the system. By cocks l5, l6 concentrated extract may be passed through a line 17 for storage and use and/or through a cooler 18 and line 19 back to the tank 2 for recycling. The cooler 18, operof the membranes (about 35C). Flow meters and pressure gauges are indicated at 22 and 23 respectively and a draw-off cock at 24.

The apparatus may be operated on a batch basis with recirculation of concentrate throughthe line 19 and rejection of the permeate at 10 to give a required concentration, or on a continuous basis with a continuous supply of fresh extract at 1 and removal of concentrated extract at 17, possibly with partial recirculation of concentrate via 19 to give a required final concentration whilst maintaining a sufficient liquid velocity through the tubes to ensure effective and efficient operation. Batch operation allows relatively small quantities of extract to be processed and the apparatus was operated in this manner for Example l described below: Example 1 48 kg of cigarette factory waste tobacco were soaked in 2.70 kg of water and the mixture was passed through a small disc refiner with a plate clearance of 0.25 mm. Extract was separated from the fibrous residue by centrifugation. A further 205 kg of water were added to the fibrous residue and the mixture was again passed through the disc refiner and subsequently centrifuged. The two batches of tobacco extract so obtained were combined and passed through a small tubular-bowl centrifuge to remove finely divided suspended matter. A total yield of 430 kg with approximately percent solids was obtained.

250 kg of this dilute extract were concentrated in the reverse-osmosis apparatus described above at a module pressure of 43 kg/cm and an operating temperature of 18 20C, giving anextract of about 24 percent concentration. A further 135 kg of dilute extract were added in the feed tank 2 and concentration was continued until the contents of concentrated extract in the apparatus were at a concentration of 28 percent.

The remaining 45 kg of dilute extract were concentrated to approximately 28 percent solids in a climbingfilm evaporator operatingat 60C and 160 mm mercury absolute pressure, to provide concentrated extract for comparative testing.

Batches of reconstituted-tobacco sheet made from flue-cured tobacco on a small Fourdrinier paper machine were cut and sprayed with the concentrates obtained by the reverse osmosis method and by the climbing-film evaporator respectively. Each of the two batches of impregnated sheet was dried under ambient conditions and then mixed with a flue-cured tobacco which is low in natural flavour at a ratio of 45 percent impregnated sheet to 55 percent tobacco. Each mixture was made into cigarettes by conventional methods and the cigarettes were smoked by a trained smoking panel. The cigarettes incorporating sheet impregnated with extract concentrated by reverse osmosis were found to have more of the smoke-flavour characteristics associated with Virginia-type cigarettes than those containing the extract concentrated by the evaporator.

Example 2 36 kg of Virginia cut tobacco were subjected to three one-hour cold-water extractions (liquid-solid ratio 10:1), the liquor being drained from the mass after each extraction. A total of 570 kg of liquor at 3 percent concentration were obtained. 500 kg of the liquor were concentrated to approximately 20 percent solids in an experimental reverse-osmosis unit using a cellulose acetate membrane operating at 39-49 kglcm pounds per square inch gauge, and room temperature. A quantity of reconstituted tobacco sheet which had been made from Virginia tobacco on a small Fourdrinier paper machine was impregnated with the concentrate so as to achieve a final soluble content in the sheet of 50 percent.

For a comparative test, 68 kg of the dilute-extract liquor was concentrated to approximately 20 percent solids in a climbing-film evaporator operating at 5060C and mm mercury absolute pressure. A second batch of the reconstituted tobacco sheet was impregnated with this concentrate so as to achieve a final soluble content in the sheet of 50 percent.

The two batches of impregnated sheet were dried under ambient conditions and were then cut and made into cigarettes by conventional methods. The cigarettes were tested by a trained smoking panel. The cigarettes incorporating extract concentrated by the process of reverse osmosis were preferred by the panel as having better taste and flavour characteristics.

Example 3 Two concentrated tobacco extracts were prepared in the manners described in Example 2. Each extract was sprayed onto a smoking mixture consisting of 33 percent of a commercially available synthetic smoking material and 67 percent flue-cured tobacco to achieve a final level of added solubles of 11 percent by weight. Cigarettes made from the mixtures thus treated were evaluated by a trained smoking panel. The cigarettes containing extract concentrated by reverse osmosis were found to have a stronger Virginia-type flavour and taste than those incorporating extract obtained with the climbing-film evaporator.

I claim:

1. A method of obtaining a concentrated tobacco extract for use in a smoking article which comprises extracting tobacco with cold water to form a dilute extract, applying the process of reverse osmosis at a pressure within the range of from 39 to 49 kg/cm to the the dilute, aqueous, extract, at a temperature from the freezing point of the extract to about 35C., using a membrane of cellulose acetate deposited on a support, which membrane is substantially impermeable to the solute components of the dilute extract.

UNITED STATES PATENT OFFICE I CERTIFICATE OF CORRECTION t t 3,847,163 Dated November 12, 1974 Inventofls) DAVID LYNEUX It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Page 1, under the heading F OREIGN APPLICATION PRIORITY DATA" delete "Germany" and substitute therefor -Great Britain.

Claim 1, Col. 4, line 50, after "to the" delete "the".

Signed and sealed this 21st day of January 1975.

[SEAL] Attest:

McCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents 8 po'wso uscoMM-oc scan-pee ILSI GOVERNMENT PRINTING OFFICE I9i9 0-366-334, 

1. A METHOD OF OBTAINING A CONCENTRATED TOBACCO EXTRACT FOR USE IN A SMOKING ARTICLE WHICH COMPRISES EXTRACTING TOBACCO WITH COLD WATER TO FORM A DILUTE EXTRACT, APPLYING THE PROCESS OF REVERSE OSMOSIS AT A PRESSURE WITHIN THE RANGE OF FROM 39 TO 49 KG/CM2 TO THE DILUTE, AQUEOUS, EXTRACT, AT A TEMPERATURE FROM THE FREEZING POINT OF THE EXTRACT TO ABOUT 35*C., USING A MEMBRANE OF CELLULOSE ACETATE DEPOSITED ON A SUPPORT, WHICH MEMBRANE IS SUBSTANTIALLY IMPERMEABLE TO THE SOLUTE COMPONENTS OF THE DILUTE EXTRACT. 